This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-337403, filed Nov. 29, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to code division multiplex (CDM) transmission systems and receivers used in such systems, and more particularly, the invention relates to a technology for synchronization and recovery of a plurality of multiplexed transmission data streams.
As widely known, in the code division multiplex transmission technology, a plurality of transmission data streams are spread frequency modulated with a spread code unique to each data stream, and those modulated signals are transmitted after multiplexed over the same carrier frequency. In such a code division multiplex transmission technique, signals modulated only by a specific spread code known to the receiving side are transmitted after being multiplexed over the same carrier frequency as that used for other spread frequency modulated signals, so that the synchronization of the spread code on the receiving side becomes easy.
In general, transmission data streams multiplexed with a spread code are subject to error correction coding and interleaving. The values of such parameters as the coding rate for error correction and interleaving length can be changed in each transmission data stream.
The convolution code and block code are used for error correction; convolution interleaving and block interleaving are used for interleaving. If the transmitting side sets selectively a punctured code for convolution coding, block code, convolution interleaving and block interleaving, the receiving side needs to synchronize the blocks and delay depth. For this purpose, synchronization words are inserted in each transmission data stream upon transmission and the data streams are synchronized by detecting these synchronization words at receiving terminals.
Although it is possible to change parameter values such as the coding rate for error correction and the interleaving length for each transmission data stream in the code division multiplex transmission mode, there is a problem that the receiving side has to continue a complex process of changing parameter values until it succeeds in receiving correct signals if the receiving side does not know the parameter values set for each data stream beforehand. As a result, it takes time to get correct signals on the receiving side.
Further, as described above, synchronization words should be inserted in the data stream for the synchronization of error correction codes and interleaving. Since different synchronization words are inserted in each transmission data stream, the detection of the synchronization word must be repeated each time the current transmission data stream is switched to another data stream. Then, a significant amount of time is consumed in this switching process.
Also in the code division multiplex transmission mode, the receiving terminal receives only one transmission data stream at a time, neglecting the other data streams. Therefore, if common information should be received in all the receiving terminals, all the transmission data streams have to carry the same information.
The present invention has been provided to solve above described problems. Its primary object is, therefore, to provide a system for code division multiplex transmission that allows the receiving side to receive correct data from an arbitrary transmission data stream in a short time even if the receiving side does not know the parameter values set for data reception in each transmission data stream.
The second object of the present invention is to provide a system for code division multiplex transmission that does not need to repeat the detection of synchronization words even if the current transmission data stream is switched to another when each transmission data stream is subject to error correction coding and interleaving and the insertion of synchronization words are necessary for parameter synchronization.
The third object of the present invention is to provide a system for code division multiplex transmission that allows all or specific receiving terminals to receive common information without incorporating the common information in all the transmission data streams even if the receiving terminals are receiving different transmission data streams.
The code division multiplex transmission system according to the present invention has the following characteristic configurations to solve the above problems.
(1) The system for transporting the spread frequency modulated signals of a plurality of transmission data streams by code division multiplexing, comprising:
a synchronization signal processing unit that generates spread frequency modulated signals as synchronization signals by time division multiplexing the signals for synchronizing spread code prepared for an easy synchronization of spread code on the receiving side and the information related to the structure or synchronization of each of the plurality of transmission data streams and by a spread frequency modulation using a spread code known to the receiving side; and
a code division multiplexing unit that generates transmission signals by code division multiplexing the spread frequency modulated signals as synchronization signals obtained in the synchronization signal processing unit over the spread frequency modulated signals of each of the plurality of transmission data streams.
(2) The code division multiplex transmission system based on the configuration of (1), wherein, the synchronization signal processing unit comprises:
a time division multiplexing unit that time division multiplexes the signals for synchronizing spread code prepared for an easy synchronization of spread code on the receiving side and the information related to the structure or synchronization of each of the plurality of transmission data streams; and
a spread frequency modulating unit that generates spread frequency modulated signals as synchronization signals by spread frequency modulating the time division multiplexed signals obtained in the time division multiplexing unit using a spread code known to the receiving side.
(3) The code division multiplex transmission system based on the configuration of (1), wherein, the synchronization signal processing unit comprises:
a first spread frequency modulating unit that spread frequency modulates the signals for synchronizing spread code prepared for an easy synchronization of spread code on the receiving side and the information related to the synchronization of each of a plurality of transmission data streams by the use of a spread code known to the receiving side;
a second spread frequency modulating unit that spread frequency modulates the information related to the structure of each of a plurality of transmission data streams by the use of a spread code known to the receiving side; and
a time division multiplexing unit that time division multiplexes the spread frequency modulated signals obtained in the first and second spread frequency modulating units.
(4) The code division multiplex transmission system based on the configuration of (1), wherein, the information related to the structure of the transmission data streams includes at least the parameter information about the coding rate of the error correction code for each of the plurality of transmission data streams.
(5) The code division multiplex transmission system based on the configuration of (1), wherein, the information related to the structure of the transmission data streams includes at least the parameter information about the interleave length for each of the plurality of transmission data streams.
(6) The code division multiplex transmission system based on the configuration of (1), wherein, the information related to the synchronization of the transmission data streams includes at least synchronization words required for the synchronization of the error correction code for each of the plurality of transmission data streams.
(7) The code division multiplex transmission system based on the configuration of (1), wherein, the information related to the synchronization of the transmission data streams includes at least synchronization words required for the synchronization of the error correction code for each of the plurality of transmission data streams; and
the transmission interval of the synchronization words is equal to the least common multiple of the least synchronization word transmission intervals required for the synchronization of the error correction code for each of the plurality of transmission data streams, and the timing of error correction coding of all the transmission data streams subject to code division multiplexing is matched with the synchronization words.
(8) The code division multiplex transmission system based on the configuration of (1), wherein, the information related to the synchronization of the transmission data streams includes at least synchronization words required for the synchronization of interleaving for each of the plurality of transmission data streams.
(9) The code division multiplex transmission system based on the configuration of (1), wherein, the information related to the synchronization of the transmission data streams includes at least synchronization words required for the synchronization of interleaving for each of the plurality of transmission data streams; and
the transmission interval of the synchronization words is equal to the least common multiple of the least synchronization word transmission intervals required for the synchronization of interleaving for the plurality of transmission data streams, and the timing of interleaving for all the transmission data streams subject to code division multiplexing is matched with the synchronization words.
(10) The code division multiplex transmission system based on the configuration of (1), wherein, the length of the signals for synchronizing spread code is longer than the maximum difference in delay in propagation paths, which is expected from multiple path propagation conditions, and the transmission interval of the signals for synchronizing spread code is shorter than the interval of the phasing fluctuation generated on transmission paths.
(11) The code division multiplex transmission system based on the configuration of (1), wherein, with regard to the synchronization signal the number of the signals for synchronizing spread code incorporated in one unit period is an integral multiple of the depth of bit interleaving conducted on each of the plurality of transmission data streams.
(12) The code division multiplex transmission system based on the configuration of (1), wherein, with regard to the plurality of transmission data streams the bit representing that the delay of the bit interleaving is zero appears at the timing right after the appearance of the signals for synchronizing spread code.
(13) The code division multiplex transmission system based on the configuration of (1), wherein, when the plurality of transmission data streams have a TS packet structure defined by the MPEG-2 systems, with regard to the synchronization signals the number of frames fit in one super frame is selected so that an integral multiple of TS packets defined by the MPEG-2 systems fit in one super frame regardless of the coding rate of the convolution code for the plurality of transmission data streams, and
the tops of the synchronization byte of each TS packet defined by the MPEG-2 systems and punctured pattern of the punctured code for the plurality of transmission data streams are set in specified positions in the first frame in one super frame of the synchronization signals.
(14) A receiving unit receiving the code division multiplexed signals transmitted by the code division multiplex transmission system based on the configuration of (1), comprising:
a decoding unit that produces the synchronization signals by decoding the received spread frequency modulated signals based on a known spread code, and
a recovery processing unit that recovers the information related to the signals for synchronizing spread code, structure or synchronization of transmission data streams from the synchronization signals produced in the decoding unit.
(15) The receiving unit based on the configuration of (14), when the information related to the structure of the transmission data streams includes at least parameter information about the coding rate of the error correction code for each of the plurality of transmission data streams, including an error correction unit that extracts the parameter information about the coding rate of the error correction code for each of the plurality of transmission data streams embedded in the information related to the structure of the transmission data streams from the output from the recovering unit, and conducts the error correction of an arbitrary transmission data stream based on the parameter information.
(16) The receiving unit based on the configuration of (14), when the information related to the structure of the transmission data streams includes at least parameter information about the interleaving length for each of the plurality of transmission data streams, including a de-interleaving unit that extracts the parameter information about the interleaving length for each of the plurality of transmission data streams embedded in the information related to the structure of the transmission data streams from the output from the recovery processing unit, and conducts the de-interleaving of an arbitrary transmission data stream based on the parameter information.
(17) The receiving unit based on the configuration of (14), when the information related to the synchronization of the transmission data streams includes at least synchronization words that are necessary for synchronization of the error correction code for each of sail plurality of transmission data streams, including an error correction unit that detects the synchronization words required for synchronization of the correction code for each of the plurality of transmission data streams embedded in the information related to synchronization for the transmission data streams from the output from the decoding unit, and conducts the synchronization of the error correction code of an arbitrary transmission data stream based on the detection timing.
(18) The receiving unit based on the configuration of (14), when the information related to the synchronization of the transmission data streams includes at least synchronization words that are necessary for synchronization of interleaving for each of sail plurality of transmission data streams, including an interleaving unit that detects the synchronization words required for synchronization of interleaving for each of the plurality of transmission data streams embedded in the information related to synchronization for the transmission data streams from the output from the decoding unit, and conducts the synchronization of de-interleaving for an arbitrary transmission data stream based on the detection timing.
(19) The receiving unit based on the configuration of (14), when the information related to the synchronization for the transmission data streams includes at least synchronization words that are necessary for synchronization of the error correction code for each of sail plurality of transmission data streams, the transmission interval of the synchronization words is the least common multiple of the shortest synchronization word transmission intervals required for synchronization of the error correction code for each of the plurality of transmission data streams, and the timing for error correction coding of all the transmission data streams subject to code division multiplexing is matched with the synchronization words,
including an error correction unit that produces the transmission interval of synchronization words by detecting the synchronization words required for synchronization of the correction code for each of the plurality of transmission data streams embedded in the information related to synchronization of the transmission data streams from the output from the decoding unit, and determines the timing of processing the error correction code of an arbitrary transmission data stream based on the transmission interval of the synchronization words.
(20) The receiving unit based on the configuration of (14), when the information related to the synchronization of the transmission data streams includes at least synchronization words that are necessary for synchronization of interleaving for each of the plurality of transmission data streams, the transmission interval of the synchronization words is the least common multiple of the shortest synchronization word transmission intervals required for synchronization of interleaving for each of the plurality of transmission data streams, and the timing of interleaving for all the transmission data streams subject to code division multiplexing is matched with the synchronization words,
including a de-interleaving unit that produces the transmission interval for synchronization words by detecting the synchronization words required for synchronization of interleaving for each of the plurality of transmission data streams embedded in the information related to synchronization for the transmission data streams from the output from the decoding unit, and determines the timing of de-interleaving for an arbitrary transmission data stream based on the transmission interval for the synchronization words.
(21) The receiving unit based on the configuration of (14), when with regard to the synchronization signal the number of the signals for synchronizing spread code incorporated in one unit period is an integral multiple of the depth of bit interleaving conducted on each of the plurality of transmission data streams,
including a bit de-interleaving unit that calculates the depth of bit de-interleaving for an arbitrary transmission data stream by counting the number of signals for synchronizing spread code included in one unit period for the synchronization signals from the output from the decoding unit and conducts bit de-interleaving of the arbitrary transmission data stream.
(22) The receiving unit based on the configuration of (14), when with regard to the plurality of transmission data streams the bit representing that the delay of each bit interleaving is zero appears at the timing right after the appearance of the signal for synchronizing the spread code,
including a bit de-interleaving unit that recognizes the bit representing that the delay of bit interleaving is zero by detecting the bit located right after the signals for synchronizing spread code from the output from the decoding unit and conducts de-interleaving of an arbitrary transmission data stream.
(23) A transmission unit for use in the code division multiplex transmission system based on the configuration of (1).
(24) A code division multiplex transmission system that transports the spread frequency modulated signals of a plurality of transmission data streams by code division multiplexing, comprising:
a synchronization signal processing unit that generates spread frequency modulated signals as synchronization signals by time division multiplexing the signals for synchronizing spread code prepared for an easy synchronization of spread codes on the receiving side and information common to all or specified receiving terminals and by a spread frequency modulation using a spread code known to the receiving side; and
a code division multiplexing unit that generates transmission signals by code division multiplexing the spread frequency modulated signals produced as synchronization signals in the synchronization signal processing unit onto the spread frequency modulation signals of each of the plurality of transmission data streams.
(25) The code division multiplex transmission system based on the configuration of (24), wherein, the synchronization signal processing unit comprises:
a time division multiplexing unit that time division multiplexes the signals for synchronizing spread codes prepared for an easy synchronization of spread code on the receiving side and information common to all or specified receiving terminals; and
a spread frequency modulating unit that generates spread frequency modulated signals as synchronization signals by spread frequency modulating the time division multiplexed signals obtained in the time division multiplexing unit using a spread code known to the receiving side.
(26) The code division multiplex transmission system based on the configuration of (24), wherein, the synchronization signal processing unit comprises:
a first spread frequency modulating unit that spread frequency modulates the signals for synchronizing spread code prepared for an easy synchronization of spread code on the receiving side by the use of a spread code known to the receiving side,
a second spread frequency modulating unit that spread frequency modulates information common to all or specified receiving terminals using a spread code known to the receiving side, and
a time division multiplexing unit that generates spread frequency modulated signals as synchronization signals by the time division multiplexing of the spread frequency modulated signals produced in the first and second spread frequency modulating units.
(27) The code division multiplex transmission system based on the configuration of (24), wherein, area identification information is included in the information common to the receiving terminals so that the terminals that can receive the common information are confined to those in specified areas.
(28) The code division multiplex transmission system based on the configuration of (24), wherein, information about the group that has been registered in advance is included in the information common to the receiving terminals so that the terminals that can receive the common information are confined to those of the subscribers belonging to the group.
(29) The code division multiplex transmission system based on the configuration of (24), wherein, an activation signal that urges the activation of receiving terminals is included in the information common to the receiving terminals.
(30) The code division multiplex transmission system based on the configuration of (24), wherein, the length of the signals for synchronizing spread code is longer than the maximum difference in delay in propagation paths, which is expected from multiple path propagation conditions, and the transmission interval of the signals for synchronizing spread code is shorter than the interval of the phasing fluctuation generated on transmission paths.
(31) The code division multiplex transmission system based on the configuration of (24), wherein, with regard to the synchronization signal the number of the signal for synchronizing spread code incorporated in one unit period is an integral multiple of the depth of bit interleaving conducted on each of the plurality of transmission data streams.
(32) The code division multiplex transmission system based on the configuration of (24), wherein, with regard to the plurality of transmission data streams the bit representing that the delay of the bit interleaving is zero appears at the timing right after the appearance of the signals for synchronizing spread code.
(33) The code division multiplex transmission system based on the configuration of (24), wherein, when the plurality of transmission data streams have a TS packet structure defined by the MPEG-2 systems, with regard to the synchronization signals the number of frames fit in one super frame is selected so that an integral multiple of TS packets defined by the MPEG-2 systems fit in one super frame regardless of the coding rate of the convolution code for the plurality of transmission data streams, and
the tops of the synchronization byte of each TS packet defined by the MPEG-2 systems and punctured pattern of the punctured code for the plurality of transmission data streams are set in specified positions in the first frame in one super frame of the synchronization signals.
(34) A receiving unit receiving code division multiplexed signals transmitted by the code division multiplex transmission system based on the configuration of (24), comprising:
a decoding unit that produces the synchronization signals by decoding the received spread frequency modulated signals with a known spread code, and
a recovery processing unit that recovers the signals for synchronizing spread code and the information common to all or specified receiving terminals.
(35) The receiving unit based on the configuration of (34), when the information common to the receiving terminals includes area identification information and the receiving terminals that can receive the common information are confined to those in the specified areas, including a common information recovering unit that extracts the area identification information embedded in the common information of the synchronization signal from the output from the recovery processing unit, separately obtains the locational information of the receiving terminal itself, judges whether the receiving terminal is located in the specified areas based on the area identification information included in the common information of the synchronization signals, and if so, receives and recovers the common information.
(36) The receiving unit based on the configuration of (34), when the information common to the receiving terminals includes information about the group that has been registered in advance and the receiving terminals that can receive the common information are confined to those of the subscribers belonging to the group, including a common information recovering unit that extracts the group identification information included in the common information of the synchronization signal from the output from the recovery processing unit, separately obtains the group registration information of the receiving terminal itself, judges whether the group the receiving terminal belongs is included in the registered group based on the group identification information included in the common information of the synchronization signals, and if so, receives and recovers the common information.
(37) The receiving unit based on the configuration of (34), when an activation signal that urges the activation of receiving terminals is included in the information common to the receiving terminals, including a reception activating unit that detects the activation signal included in the common information of the synchronization signals from the output from the recovery processing unit and activates the reception process based on the activation signal.
(38) The receiving unit based on the configuration of (34), when with regard to the synchronization signal the number of the signals for synchronizing spread code incorporated in one unit period is an integral multiple of the depth of bit interleaving conducted on each of the plurality of transmission data streams,
including a bit de-interleaving unit that calculates the depth of bit de-interleaving of an arbitrary transmission data stream by counting the number of signals for synchronizing spread code included in one unit period for the synchronization signals from the output from the decoding unit and conducts bit de-interleaving of the arbitrary transmission data stream.
(39) The receiving unit based on the configuration of (34), when with regard to the plurality of transmission data streams the bit representing that the delay of each bit interleaving is zero appears at the timing right after the appearance of the signal for synchronizing the spread code,
including a bit de-interleaving unit that recognizes the bit representing that the delay of bit interleaving is zero by detecting the bit located right after the signals for synchronizing spread code from the output from the decoding unit and conducts bit de-interleaving of an arbitrary transmission data stream.
(40) A transmission unit for use in the code division multiplex transmission system based on the configuration of (24).
Namely, for attaining the above first to third goals, the code division multiplex transmission system according to the present invention, focusing attention on that all the receiving terminals receive the signal modulated only with a specific spread code (hereafter xe2x80x9cspread code for synchronizationxe2x80x9d) known to each receiving terminal in addition to transmission data streams so that the synchronization process of the spread code becomes easy to conduct at each receiving terminal. The system of the present invention spreads with the spread code for synchronization at least one kind of information out of parameters information referred to in the first goal such as the coding rate of the error correction code and interleaving length for each transmission data stream, information about synchronization words referred to in the second goal necessary for the synchronization of the error correction code and interleave of each transmission data stream and information common to all or specified receiving terminals referred to in the third goal (hereafter those kinds of information are referred to as xe2x80x9cparameters etc.xe2x80x9d), time division multiplexes these spread frequency modulated signals of parameters etc. over signals modulated only with the spread code for synchronization, and then multiplexes these time division multiplexed signals as synchronization signals over the same frequency as that of the spread frequency modulated signals of the transmission data streams.
During the above time division multiplexing, in order not to cause problems in the synchronization process of the spread code at receiving terminals, the length of the signal for synchronizing the spread code is set longer than the maximum difference in delays in propagation paths which is expected from the multiple paths conditions, and the transmission interval of the signal for synchronizing the spread code is set shorter than the fluctuation periodicity of phasing in propagation paths.
Further, the above transmission interval of synchronization words is set to be the least common multiple of the minimum transmission intervals of synchronization words required for the synchronization of parameters such as the error correction code and interleave of each transmission data stream, and thereby the timing of the error correction coding and interleaving of all the transmission data streams subject to code division multiplexing is matched with that of synchronization words.
The above configuration allows all the receiving terminals to receive parameters etc. along with transmission data streams without causing a problem in the synchronization process of the spread code at each receiving terminal. As a result, the decoding of the error correction code and de-interleaving of each transmission data stream can be performed easily and quickly, by the use of the received information about the coding rate of the error correction code and interleave length of each transmission data stream.
In addition, since the timing for the error correction coding and interleaving of each transmission data stream matched with that of synchronization words, synchronization is not necessary to be redone for the reception of another transmission data stream and consequently the synchronization of the error correction coding and interleaving of each transmission data stream is facilitated. Also since the redo of synchronization becomes unnecessary, the time for changeover to the reception of another transmission data stream can be shortened.
Besides, information common to all or specified receiving terminals is constantly received by all or specified receiving terminals, the common information can be sent to all or specified receiving terminals without sending the same information to all the transmission data streams.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.